Is it bad to dump water on yourself while exercising?

Cool water does tell the body that you are cooling and to slow or stop the circulation of blood the the surface to conserve heat. Secondly cool water also sends the false signal to stop sweating. Neither is a good thing, if you are severely overheated water at ambient temp. will cool by evaporation and help with out the effects of over cooling. While racing I'll keep a bottle to pour on my self but the bottle is at air temp, never cold. I never pour water on my legs during a race and do it sparingly after wards. If you are on the verge of heat exhaustion then things change and you need to get off the bike in shade and cool down.